Most developing countries politically drive forward industrial development and rapid growth with little thought for the protection of the environment, thus resulting in environmental disruption. In most countries with developed architectural and public civilization, reconstruction produces rebuilding waste articles, such as earth, sand, waste brick, waste concrete, waste wood and waste asphalt which have to be effectively treated and recycled, thereby conserving resources and protecting the environment.
Therefore, it is time to provide measures to effectively treat such waste articles and pollutants, produced in countries driving forward a high-growth policy.
Particularly, the amount of construction waste articles, produced from building or public works, is rapidly increased in most countries since some urban or local areas in such countries include superannuated buildings, which compromise the safety of residents and fail to meet newly required residential functions, thus needing reconstruction.
As well known to those skilled in the art, construction waste articles typically include various materials such as earth, sand, pebbles, stones, waste brick, waste concrete, waste wood, waste asphalt and sludge. A characteristic of such construction waste articles is that the articles have an inorganic composition which is not harmful to the human body. However, due to the various materials included among construction waste articles, it is somewhat difficult to effectively treat and recycle the waste articles. Such difficulty in treatment for the construction waste articles is a cause of the indifference of most governments and companies toward the recycling of such waste articles.
The indifference of the governments and companies toward the recycling of construction waste articles results in waste of resources and reduction in quality of recycled articles which have been reutilized in some way. In this regard, such construction waste articles are just used as a material for raising the ground or reclaiming land and it is a matter of regret.
Therefore, it is necessary to actively strive for the appropriate treatment and recycling of such construction waste articles in an effort to achieve the protection of the environment, the conservation of resources and the reduction in construction expenses.
In order to meet the above necessity, some countries make or improve related laws and regulations in such a way to force related industries to recycle construction waste articles and provide various systems for recycling such waste articles.
Such an obligation to recycle construction waste articles results in the development of various systems capable of partially or totally processing such waste articles so as to reutilize the waste articles.
As an example of known systems for recycling construction waste articles, movable crushers, capable of recycling the waste articles, are used at building or public works. However, such known movable crushers are problematic in that they can not effectively treat the waste articles, including various materials, and fail to provide a desired quality of recycled articles.
Another problem of the above crushers is that the crushers are similarly designed and manufactured while disregarding the different characteristics of construction waste articles to be treated by the crushers. The operational effect of such crushers is thus reduced and this limits use of the crushers.
Korean Utility Model Publication 94-4771 discloses a system for treating and recycling waste articles. In the above Korean system, waste articles fall by their weight while being processed at a plurality of steps of, for example, dividing the falling articles into metals and nonmetals, cutting the metals and nonmetals into pieces and collecting earth or dust from the pieces, thus more effectively collecting usable articles and conserving resources.
In order to accomplish the above-mentioned operational effect, the Korean system comprises a waste inlet opening, a first conveyor, a first roller crusher, a first magnetic conveyor, a cutter, a first screen, a second roller crusher, a second conveyor, a second magnetic conveyor, a second screen and a third conveyor (a horizontal conveyor) which are arranged in order. The system also has an inclined frame with the waste inlet opening being formed at the top portion of the frame. The first roller crusher comprises a set of shafted rollers of which the outer surfaces are uneven, thus crushing the waste articles. The first magnetic conveyor comprises a electromagnetic roller, a nonconductive/nonmagnetic roller and a cylindrical pipe. The cutter comprises two blades: a fixed blade and a movable blade.
Japanese Patent Publication No. Hei. 5-21632 discloses a waste article treatment system. This Japanese system comprises a press and a crusher which are respectively used for compressing and crushing waste articles. The above system also includes a separator and a furnace. The separator is for dividing the compressed and crushed waste articles into classes, while the furnace is for melting the grouped articles prior to forming the melted articles into determined shapes using molds. The formed articles are, thereafter, discharged from the system by a conveyor belt. Another example of the typical waste article treatment is referred to in Japanese Patent Publication No. Hei. 6-30755 which discloses a method and system for recycling waste concrete. The method and system disclosed in the above Japanese patent is for crushing waste concrete into pieces having a size suitable for allowing the concrete pieces to be usable. In the operation of the above system, waste concrete is crushed into pieces by a cylindrical drum. The drum has a plurality of crushing protrusions on the internal surface and is eccentrically rotatable by a motor. Crushed pieces, having a predetermined size, fall onto a conveyor belt by their weight prior to being discharged from the system. Meanwhile, the other pieces and powders, which are non-standardized, are fed to intermediate steps through another conveyor belt, which is arranged at the top portion of the drum. The non-standardized pieces and powders are processed at the intermediate steps and are discharged from the system. On the other hand, finely ground powders are processed at a retreating step and are classified into groups prior to being appropriately reutilized.
However, the typical methods and systems for treating and recycling construction waste articles fail to effectively classify the waste articles, thus regrettably reducing quality of recycled articles. The operational effect of the known recycling systems is too low to be generally used in various industrial fields.
In addition, a system for recycling waste articles including dredged mud is proposed and used at various industrial fields.
The above system continuously processes waste articles, including dredged mud, at a plurality of steps: a crushing step, a selecting step and a washing step, thus collecting usable articles. However, the system is problematic in that it fails to effectively or automatically select useless materials from the waste articles due to a defect in the mechanism or the arrangement of the system's parts. Such a defect also causes both a screen and a conveyor belt to often break down during the operation of the system and results in contamination of water used in the washing step, thus forcing the water to be treated through a complex process.
Another problem experienced in the above system is that a rotatable drum, used as a selector for selecting useless materials from the waste articles, easily catches vinyl pieces, fabric pieces or synthetic resin pieces. It is thus necessary to burn such articles, caught by the selector, using a torch lamp. The above system may use a blowing effect for selecting useless materials from the waste articles on the conveyor belt. That is, a blower may be arranged at a position under the outlet end of the conveyor belt and blow around the articles dropped from the outlet end of the conveyor belt, thus selecting the useless materials by specific weight of the materials. However, such a blower fails to effectively select the useless materials since the waste articles form a curtain when they are dropped from the outlet end of the conveyor belt.
In this regard, the selection of useless materials from the waste articles on the conveyor belt has to be manually performed. That is, the useless materials have to be manually selected by many workers standing around the conveyor belt. In such a case, a water tank is added to the system and supplies water to the conveyor belt, thus washing the waste articles on the conveyor belt.
In the above system, waste articles may be double processed. That is, the waste articles may be subjected to primary and secondary processes individually including a crushing step, a selecting step and a washing step. After the secondary process, the recycled articles are discharged from the system through a vertical discharging method. However, since construction waste articles typically include various useless materials, such as wood, paper, plastic materials, vinyl pieces, synthetic resin materials and styrofoam pieces, the process of recycling such construction waste articles exceedingly wastes time and labor and fails to provide high quality recycled articles.
As well known to those skilled in the art, waste concrete amounts to at least 30% of all construction waste articles.
For example, Korea, a developing country, generates about 10.sup.7 tons (43.times.10.sup.5 m.sup.3) of waste concrete, about 7.times.10.sup.6 tons of waste asphalt concrete, about 58.times.10.sup.5 tons of construction sludge, about 3.times.10.sup.6 of waste wood and about 58.times.10.sup.5 tons of mixed waste articles for a year.
According to the above statistics, it is noted that waste concrete accounts for at least 1/3 of all construction waste articles generated in Korea.
FIG. 1 shows a typical process of producing recycled aggregate using such waste concrete. As shown in the drawing, waste concrete is primarily crushed into pieces, having appropriate sizes meeting the capacity of a crusher, prior to being processed by a recycling system. In the recycling system, the waste concrete is crushed by a jaw crusher having a capacity of 100 t/h prior to being processed through a selecting step of separating reinforcing steel pieces and waste wood from the waste concrete. The waste concrete is, thereafter, crushed by an impact crusher having a capacity of 100 t/h and is processed by a magnetic selector which finally selects reinforcing steel pieces from the waste concrete. The waste concrete from the magnetic selector is screened, thus being classified into several groups of recycled aggregate having different sizes.
However, the process of FIG. 1 is problematic in that the recycled aggregate is too rough to reutilize. Typically, the characteristics of recycled aggregate are changed in accordance with the sizes of the aggregate in a way such that specific weight and moisture absorption of the aggregate are respectively reduced and increased in inverse proportion to the size of the aggregate. The recycled aggregate, produced by the process of FIG. 1, has a small size, thus including a large amount of cement paste. Such cement paste reduces the quality of the recycled aggregate.
It is, therefore, necessary to more effectively recycle construction waste articles, such as earth, sand, waste brick, waste concrete, waste wood and waste asphalt, produced from building or public works, and to produce high quality recycled aggregate and to conserve resources.
Of course, such a recycling of construction waste articles has to be free from the generation of contaminants.